This invention relates to a process for the prevention of popcorn polymer in organic materials by treating said material with at least one inhibitor selected from white phosphorus and carbon disulfide.
Popcorn polymer formation in organic materials containing vinyl compounds has long been known. Popcorn polymer is characterized by a white opaque voluminous structure always insoluble in the system where it is formed, as described, e.g., in Advances in Macromolecular Chemistry, Vol 1, Academic Press, N.Y. (1968), pp. 139-169 incorporated herein by reference.
Other names proposed in the literature for the instant popcorn polymers include sponge polymer, granular polymer, nodular polymer, cauliflower-like polymer, proliferous polymer, fluffy polymer and crusty polymer.
A characteristic of this polymer is its remarkable growing ability, i.e. it is able to consume and transform e.g. a vinyl compound into a popcorn phase without the need for an initiator and/or a cross-linking agent.
Growth of the polymer in industrial processing equipment can be disruptive of operations e.g., by plugging of tubular equipment such as heat exchangers and the like. Uncontrolled, the growing popcorn polymer has been known to exert tremendous force actually bulging heavy walled equipment, and bending and distorting trays and support beams within fractionation distillation equipment. Of great concern is that such polymer once active in industrial equipment is extremely difficult to deactivate and even trace quantities which remain on equipment after a clean-out, will remain active for long periods after being removed from the monomer, and act as seed to resume polymer growth when again in contact with the vinyl monomer. Manifestly such a problem is of deep concern in the operation of vinyl compound purification processes, particularly in processes designed for the separation of polymerization grade conjugated diolefins such as butadiene and isoprene from other organic materials such as mixtures of hydrocarbon resulting from cracking of petroleum and the like.
Over the years a number of materials have been suggested for inhibiting popcorn polymer growth including e.g. hydrogen sulfide (from hydrolysis of aqueous potassium sulfide) ethane-, propane- and hexane-thiol and to a lesser degree ethyl disulfide, however, these have not found wide application in the industrial processes.